1. Field of the Invention
The invention relates to a process for producing novel photosensitive resins. More particularly, the present invention relates to a process for producing photosensitive resins having cinnamic groups ##STR2## introduced into the side chains of a polyallylamine.
2. Description of the Prior Art
Many papers have hitherto been issued on the synthesis of photosensitive resins having cinnamic acid moieties at the side chains. The synthesis is largely divided into the following two processes.
One is a process wherein a vinyl compound having a cinnamic acid moiety is synthesized and the compound as a monomer is then polymerized to obtain a photosensitive resin. The other is a process wherein an appropriate resin selected as a support is reacted with a compound having a favorably modified cinnamic acid moiety to obtain a photosensitive resin.
As an example of the photosensitive resins produced according to the former process, there is widely known polyvinyl cinnamates obtained by polymerization of vinyl cinnamate, disclosed in U.S. Pat. No. 2,610,120 granted to Eastman Kodak Co. in 1952.
The former process, however, have drawbacks as follows. During the synthesis of the monomer, there occur side reactions such as partial polymerization of the monomer making the isolation and purification of the monomer more complex. Further, when the resin obtained is used in certain applications, the resin, having an unnecessarily large number of active sites, becomes hard and brittle after photocuring.
As an example of the photosensitive resins produced according to the latter process, there are photosensitive resins obtained by reacting a polyvinyl alcohol with a cinnamic acid chloride. These resins occupy the most part of the market of the latter photosensitive resins.
The above resins have problems with respect to, for example, the solvent used at the time of development thereof.
In photoresists of a polyvinyl cinnamate, for example, there is used a developping bath containing an organic solvent, but an aqueous developping bath is desired from the standpoint of the safety of working environment.
To improve the situation, attempts are under way to modify the resins so as to be soluble in aqueous alkali solutions, preferably in water. Examples of the modification include the introduction of carboxyl group into the resin [Kodak Co., U.S. Pat. No. 2,861,058 (1958)], the introduction of phenolic hydroxyl group into the resin [Fuji Yakuhin Kogyo K. K., Japanese Patent Publication No. 44601/1974] and the introduction of sulfonic acid group into the resin [UNITIKA, LTD., Japanese Patent Application Kokai (Laid-open) No. 55282/1973]. These modifications, however, require one additional production step making the process more complex and the product cost higher.